I. Field
The following description relates generally to wireless communications, and more particularly to frequency offset between adjacent carriers.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple mobile devices. Each mobile device can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to a mobile device. A mobile device within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, a mobile device can transmit data to the base station or another mobile device.
Orthogonal Frequency Division Multiplex systems use a set of individual frequency tones to carry modulated information. The tones are made orthogonal by a certain relationship between the time duration of the useful part of the OFDM symbol and the offset between the tone frequencies. To keep all tones orthogonal, the symbol duration, before the cyclic prefix insertion, is typically chosen to be the reciprocal of the tone spacing, which is the frequency offset between adjacent tones. As long as two signals occupying different set of tones are received with small time offsets, the orthogonality between the composite signals can be maintained.